Electric valve translating apparatus



Sept. 18, 1945. o. w. LIVINGSTON ELECTRIC VABVE TRANSLATING APPARATUS Filed April 25, 1942 2 Sheets-Sheet l y Inventor: Orrin W, Livingston,

- Hi Attorney.

Sept. 18, 1945. o. w. LIVINGSTON ELECTRIC VALVE TRANSLATING APPARATUS Filed April 23, 1942 2 Sheets-Sheet 2 mm a m, 1% 2 n w 3? v A T. I O

b NmE Patented Sept. 18, 1945 ELECTRIC VALVE TRANSLATING v APPARATUS Orrin W. Livingston,

General Electric Co New York Scotia, N. Y., assig'nor to mpany, a corporation of Application April 23, 1942, Serial No. 440,160

12 Claims.

My invention relates to electric translating apparatus and more particularly to electric valve translating apparatus for interconnecting an alternating current supply circuit and a direct current load circuit.

' In some industrial applications, it is important to provide equipment for supplying relatively heavy direct currents to an associated load circuit where the source of energy is alternating current. In accordance with the teachings of my invention described hereinafter, I provide new and im-- proved electric valve apparatus wherein relatively large or heavy unidirectional currents may be transmitted to a load circuit and wherein not only the magnitude of the current transmitted to the load circuit is accurately determinable, but the period of time or interval of energization of the load circuit is precisely controllable or adjustab e.

It is an object or my invention to provide new and improved electric valve translating systems.

It is another object of my invention to provide new and improved control systems for electric valve translating apparatus.

It is a further object of my invention to provide new and improved control systems for electric valve translating apparatus wherein the energizetion of a direct current load circuit is accurately controllable during predetermined intervals of time.

It is a still further object-of my invention to provide new and improved electric valve translating apparatus for interconnecting alternating current and direct current circuits.

It is a still further object of my invention to provide new and improved control systems for electric valve translating apparatus wherein a direct current load circuit may be periodically energized from a source of alternating current, and wherein the system operates to eflect such periodic or intermittent energization of the load circult in a manner to prevent the occurrence of transient starting currents.

Briefly stated, in one of the illustrated em bodiments of my invention I provide an electric valve translating system for energizing a direct current load circuit from a polyphase alternating current supply circuit. Polyphase transforming means may be employed and a plurality of pairs of reversely connected electric valve means are connected between different phases of the supply circuit and the transforming means for transmitting thereto alternating current. Rectifying means, such as a plurality of biphase rectiilers, are connected between the transforming means and the load circuit. The pairs of electric valve means are provided with associated control or excitation circuits and include means for rendering the respective pairs of electric valve means conductive in a predetermined order or sequence in a manner so that any one pair conducts current during a period of time during each cycle of voltage of the supply circuit not less than 60 electrical degrees and not greater than 120 electrical degrees, thereby assuring the desired accuracy of the energization of the load circuit.

In another embodiment of my invention diagrammatically illustrated, I provide an arrangement wherein unidirectional current is transmitted to a direct current load circuit from a polyphase alternating current supply circuit.

Timing means, such as an electric valve inverter, is provided for efl'ecting a single energization of the load circuit for a predetermined time, or for effecting intermittent or periodic energization of the direct current load circuit. Pairs of reversely connected electric valve means are connected between transforming means and different phases of the supply circuit, and rectifying means are connected between the load circuit and the transforming means. Additional means are also provided for controlling the conductivities of the pairs of reversely connected electric valve means so that initiation of conduction of the respective pairs of electric valve means begins durin the respective phase voltages at times corresponding to the power factor angle of the load imposed on the supply circuit, thereby eliminating the start ing current transients.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims. Fig. 1 diagrammatically illustrates an embodiment of my invention as applied to a system for energizing a direct current load circuit from a three phase alternating current supply circuit. Fig. 2 diagrammatically illustrates another embodiment of my invention wherein periodic energization of a direct current load circuit is obtained, and wherein the system is controlled to lessen the duty imposed on the supply circuit.

Referring now to Fig. l of the accompanying drawings, my invention is there diagrammatically illustrated as applied to a system for energizing a direct current load circuit, such as a welding circuit i, from a polyphase alternatin current supply circuit 2. Polyphase transforming means, such as transformers 3; 4 and 5, are connected to be energized from different phases of the supply circuit 2 through pairs of reversely connected electric valve means 6 and i, 8 and 9, and i and ii. The electric valve means t-l i, inclusive, are connected to transmit alternating current to the associated transforming means, and the energiza-tion of each of the transforming means 3-5 is obtained by current flow through the various pairs of electric valve means.

Transformers 3-5 are each provided with primary winding means l2 connected to the different phases of the supply circuit 2 through associated pairs of electric valve means and each includes secondary winding means l3 which, cooperating with rectifying means it and 55, constitute a biphase rectifier for transmitting direct current to the welding circuit i. The rectifying means l4 and i5 may be of the dry type, such as copper oxide rectifiers, and may be designed to comprise a plurality of rectifiers in parallel, series, or series-parallel relation in order to satisfy the load requirements. It will be noted that three biphase rectifiers are employed and that the rectified output currents thereof are displaced in accordance with the phases of the voltages applied to transformers 3-5, inclusive. Voltage limiting means are associated with transformers 3-5, inclusive. These voltage limiting means may comprise devices connected across the primary winding means [2. I may employ voltage limiting means, such as resistances i6, having negative nonlinear current-voltage characteristics.

The electric valve means fi-li m the type employing an ioniaable rr as a gas or a vapor, and each com. I H, a cathode i8 and a control means be an immersion-igniter control ciated with the cathode and constructed of a material such as boron-carbide or silico bide so that when sufilcient current is mitted thereto the medium of the electric means is ionized and the electric valve means conducts current. Transformer 3 is connected to one phase of the supply circuit 2 through. electric valve means 6 and l, conductor 23, conductor 2i and electric valve means 8 and. Tran"- former 4 is connected to another phase of the supply circuit 2 through electric valve means 8 and l, conductor 20, conduct-or electric valve means I and ii. Transformer connected to a still different phase of the supply circuit 2 through electric valve means 8 and 8, conductor 2|, conductor 22 and electric valve means it] and i I.

I provide a plurality of excitation circuits 23-28, inclusive, associated with electric valve means 6-H, respectively. These excitation circuits are similar in construction and arrangement and in order to facilitate description of my invention, only excitation circuit '23 will de scribed in detail. Referring to excitation circuit 23, I provide a control electric discharge device 29 which is employed for energizing the control member 19 of the electric valve means 8 and which when in a conducting condition transmits unidirectional current to the control n mber is from the associated phase of the supply circuit 3. The electric discharge device 29 'may be of the type employing an ionizable medium. such as a gas or a vapor, and may nclude a control means such as a control grid 30 the potential of which controls the current conducted by the discharge device. A further control grid, such as a shield grid 3!, may be connected to the cathode, and a til transient voltage absorption means, as a capacitance 32, may be connected between the control grid 36 and the cathode.

I also provide in excitation circuit 23 means for impressing on grid 30 a biasing potential, such as a negative unidirectional biasin potential, to maintain the electric discharge device 29 nonconducting except during predetermined times during the cycle of the associated phase voltage. This means may comprise a capacitance 33 which is energized from a transformer 34 energized by a suitable source of alternating current described hereinafter. A suitable rectifying means, such as an electric valve 35, may be connected in circuit with the capacitance 33 and the secondary winding of transformer 34. I provide control or adjusting means, such as an adjustable resistance 36, connected in series relation with the rectifier 35 and the capacitance 33 to control the magnitude of the negative unidirectional biasing-potential and thereby afford a means for controlling the period of time during each cycle of phase voltage of the supply circuit 2 during which the electric valve 6 may he initiated in its conduction of current. A discharge path comprising a resistance 31 is connected across the capacitance 33. Transformers 38 and 39 may be employed as sources of cathode energizing current for the filaments of the electric discharge device 29 and the electric valve 35. It will be understood that instead of using an electric valve of the discharge type, I may employ in place of the electric valve 35 a rectifier of the dry type.

In order to control precisely the time at which the electric discharge device 23 and, hence, the electric valve means 5 are rendered conducting during the cycle of associated phase voltage, I provide a transformer 43 connected in circuit with the cathode and the grid 30 of electric discharge device 23. This transformer, if desired, may be of the type designed to produce an alternating or periodic voltage of peaked wave form, thereby obtaining the desired precision and accuracy in the control of the electric discharge device 23 and electric valve means 6.

The above description relating to excitation circuit 23 also applies to excitation circuits 24-28. It will he noted that these excitation circuits also include adjustable resistances H45, inclusive, which control oraiolish the desired times of initiation or conduct n by the associated electric valve means "l -ii, respectively. More particularly, resistances 35 and 4 I45, inclusive, are controlled so that each pair of electric valve means may he initiated in conduction at times during the cycle of associated phase voltage for a period or interval of time less than 60 electrical degrees. In this manner, proper energization of transformers 3-3:: is obtained since it is desired to transmit to these transformers three phase alternating current during the intervals of time in which it is desired to effect energlzation of the welding circuit Polyphase alternating current is transmitted to transformers 4d oi excitation circuits 23-28, inclusive, from 9, suitable source of alternating current which may be derived from the supply circuit 2 through transformers 5 and H which may be connected in a conventional open delta. The

output circuit 48 of these transformers may be connected to suitable phase shifting means, such as a rotary phase shifting device 49, which permits control or adjustment of the phase of the voltages applied to transformers 40 and, hence,

controls the time during the cycles of voltage applied to electric valve means 6-H at which these electric valve means are rendered conduct ing. Consequently, the phase shifting device t9 affords an arrangement for controlling the amount of current transmitted to the welding circuit I. If desired, a relay 50 may be connected between the phase shifting device 49 and transformers 40 to disconnect the source of alternating current therefrom. Actuating coil of relay 50 may be controlled by means of a. switch 52.

I provide means for simultaneously controlling the excitation circuits 23-28. This means may comprise a plurality of circuit controlling means arranged to render the excitation circuits 23-28 operative simultaneously in response to a single circuit controlling operation. For the purpose of illustration, I have chosen to represent this circuit controlling means as comprisinga contactor or relay means 53 comprising contacts 54-59, in elusive, and including an. actuating coil 80. The relay 53 may he designed so that the contacts 54-58, inclusive, are biased to the open circuit position when the actuating coil 60 is not energized. Time delay means, such as a relay 8|, may be employed to prevent operation of the relay 53 until the filaments of the electric discharge devices employed in the system have assumed safe operating temperatures. An interconnecting relay 62 may be connected between relay 6! and the circuit for energizing actuating coil 60 so that upon operation of relay Bl, relay 62 closes its contacts assuring energization of the actuating coil 60. A suitable timing means, such as a relay 83 having contacts 64 in series relation with the actuating coil 60, is employed for effecting energization of the actuating coil 50 for a predeter mined interval of time at the expiration of which relay 83 opens its contacts 64, thereby effecting deenergization of the coil 60 and consequently opening contacts 54-59. Manually operable means or automatic means may be employed for controlling initiating switch 65. If desired, the relay 63 need not be employed, and the period of energization of the welding circuit i may be controlled by a switch 66 which is connected in series relation with the acuating coil 60 Oi course, if desired, the switch 88 maybe employed and maintalned in the closed circuit position so that the controlling operation is obtained by use of relay 63 and switch 65.

The operation 01' the embodiment of my inven tlon shown in Fig. 1 will be explained .by considering the system when it is operating to eilect energization of the welding circuit l for a predetermined interval of time. Upon energization of the supply circuit 2, the various filaments for the electric discharge devices will he energized and upon the expiration of the predetermined interval or time established by relay 6i, relay 62 will close its contacts, thereby placing the system in condition for operation. Upon closure of switch 52, relay 5!) is closed and the source of alternating current for energizing transformers 40 is effectively connected to excitation circuits lit-lit, in" elusive. The electric valve means S-i l, inclusive, are maintained nonconducting by virtue of the fact that the anode-cathode circuits for electric discharge devices 29 are open. Upon closure of switch 65, switches 68 and 52 being in the closed circuits positions, actuating coil of relay 53 is en ergized, effecting simultaneous closure of contacts 54-59 and thereby rendering excitation circuits 23-28 in condition for operation.

ilii

, H1, 1 l0, 9. It will thus be appreciated that c various of are selectively controlled 23-28, so that these elect current in a predetermir valves of each pair conduct current c vals of time displaced 180 electrics tive to the voltage of the supply circuit a. one time two electric valves conduct c For example, the following electric valves current simultaneously during succeeding Bil trical degree intervals: 6, 9; 8, ii; 8, ii; a,

electric valve conducts current for electl degrees but for only 60 electrical degrees wit one other electric valve. The excite." on 23-28 establish a period of t which each electric valve means in its conduction of current. i the excitation circuits establish a n of 6!) electrical degrees rela supply circuit 2 Hi ated. The control to estahi. is tained by adlustment of resistances as no a, inclusive.

Alternating current is transmitted to trar formers 3-5, inclusive, by the electric valve 6-H which conduct current in a piece order. Rectifiers l4 and i5 rectif ing voltaget appearing across the t secondary winding means H to tional current to the welding circi...

At the expiration of the period c lished by relay 63, contacts 66 are or effecting deenergization of actuat causing contacts 5 i-5Q to ope the excitation circuits 23-28 are 1 further operation. and consesuentl means G-t are prevented from c manner, the p ing circuit 1 is terminated at reflected nergization of the welding eirc predetermined interval of time.

I! it is desired, the period of energizatio Welding circuit 5 may be controlled by of switch 52', in which case it will he that excitation circuits 23-28, inclusive, the d'mcharge devices the closure of switch 52, altez are impressed on grids 3t of disc 29, thereby rendering "the clicclr' ducting at the desired times. the switch 52 is employed, it Wiil in that relay 53 and switch ti? need. not played.

Fig, 2 diagrams "zicaily bodiment of my invention for energizing the welt supply cit 'YJhe pairs tie t a. (i and "i, ii and i and it and n between different phases of the s g and polyphase transforming transformers S'l, t8

cult i. transformer 13, having ind 'ctive ings M, iii and 15 conn '1 i with the output circuits of high respectively. 'These windings serve to prevent back excitation on pairs of electric valve means occasioned by conduction of another pair or electric valve means so that the conduction by electric valve .means may be initiated at the proper point in the cycle of alternating voltage, thereby assuring accurate energization of the welding circuit I.

I employ electric discharge devices II-82, in-

clusive, associated with electric valve means -I I,

respectively, for controlling the energization oi the control members I0 thereof. Discharge devices I142, inclusive, may be of the type employing an ionizable medium, such as a gas or a vapor, and each isprovided with a control grid at. The anode-cathode circuits of discharge devices "-82 are connected between the anodes and the control members I0 oi the associated electric valve means. The potentials of control grids II are normally maintained negative, thereby preventing conduction by the electric discharge devices except during those intervals when conduction is desired. The biasing potentials may be Provided by suitable means such as batteries 84.

In order to control selectively the conductivitles of the various pairs of associated electric valve means to render the electric valve means conducting in a predetermined order or sequence by controlling the energization of the control members I 0, I provide a plurality of individual control circuits 85, 86 and 81. Control circuits "-01 control the application of energizing voltage to grids 82 of discharge devices II-02. Control circuits 05-81 include electric discharge devices 00 and 09, 00 and SI, and 52 and 93, respec' tively. The voltages impressed on grids 83 of discharge devices 11-82 are preferably voltages of peaked wave form, and voltages of this type may be provided by means of saturable peaking transformers 94, SI and 98 which selectively connect the grids of the discharge devices associated with the respective pairs of electric valve means to control circuits 0!, 86 and 81, respectively. The control circuits 85, 06 and 81 are coupled to the grid circuits of discharge devices IT-82 through transformers lI-I02. As a means for controlling the magnitude of the current transmitted to the welding circuit I, I provide means for controlling the phase of the voltages impressed on the grids l3 oi the electric discharge devices 11-82. More particularly, I may employ suitable phase shifting means such as a rotary phase shifter I03 which is connected between the supply circuit 2 and the primary windings of peaking transformers 40.

I provide timing means for generating an electrical quantity to control the period of energization of the welding circuit I. Furthermore, the timing means may be controlled by additional means described hereinafter to generate an electrical timing quantity so that the period of energization of the welding circuit I is controlled as well as the period Or interval of time between each energization of the welding circuit. More specifically, I provide a timing means III which may be of the inverter type comprising a pair of electric discharge devices I05 and I06. These discharge devices may also be of the type employing an ionizable medium and each comprises an anode I01, a cathode I08 and a control means such as a grid I09. The timing means I04 may be energized from a suitable source of direct current comprising a positive conductor H0 and a negative conductor HI. The source may be supplied by a suitable rectifier I I2 energized from the supply circuit 2 and may include a filtering circuit including an inductance II! and a capacitance Ill.

The timing means I may be arranged so that when the discharge device I00 is conducting a negative voltage is produced, thereby maintaining the electric discharge devices 00-" nonconducting and thereby preventing energization of the welding circuit I. A positive impulse of voltage is produced when current is commutated from discharge device I00 to discharge device I", thereby rendering the discharge devices "-00 conducting and causing energization of the weld ing circuit I for a period oi time determined by the time constants oi the timing means I04.

The timing means III is essentially an electric valve inverter comprising two electric valve means, both of which are energized from a direct current source including conductors III and I II through a common resistance H0. In series relation with the anode-cathode circuits of electric discharge device I05, I employ impedance elements such as resistances II and III, and in series relation with the anode-cathode circuit of discharge device I 00 I connect a resistance III. In order to commutate the current between discharge devices I05 and I0, a commutating capacitance H8 is employed and is preferably connected between the anodes or the discharge devices.

To control the time during which a positive voltage is produced by the timing means I04, I

connect a capacitance I20 in circuit with resistance III and grid I09 oi the discharge device I06. A discharge circuit for the capacitance I20 is provided and includes a resistance I2I, winding I36 and a portion of resistance I22. The duration of time during which the control voltage produced by circuit Illl is positive is determined by the time that the discharge device I08 is nonconducting, or the period ci' time that the discharge device I05 is conducting. Adjustment of resistance II1 establishes the time during which the discharge device I00 is nonconducting.

The time at which the positive portion of the electrical timing quantity produced by circuit I0! is initiated is determined at the time discharge device I00 is rendered nonconducting. A suitable component 01' unidirectional voltage is impressed on grid I09 r discharge device I00 from a voltage divider comprising a resistance I2I and a resistance I22. This voltage cooperates with a voltage of peaked wave form, described hereinafter and accurately initiates conduction by discharge device I00.

The timing circuit I04 and the capacitance controlling circuit therefor for controlling the conductivities of associated electric discharge devices are disclosed and claimed in my copending patent application Serial No. 440,159, filed concurrently herewith, now United States Letters Patent 2,348,553, granted May 9, 1944, and assigned to the assignee of the present application.

So that the initiation o! conduction by the various pairs of electric valve means 0-H is initiated at times during the respective cycles of the phase voltages which will not cause starting current transients, I provide means for assuring control of the time of initiation oi conduction by the electric valve means. This means may be connected to the control circuits 05-01 and may comprise electric discharge devices I 23, I20 and I25. The discharge devices III-I 25 are associated with, and control circuits I1, I and II, and consequently control the time at which initiation of conduction is initiated by the respective associated pairs of electric valve means. To control precisely the conductivities of electric discharge device I23-I25, I provide suitable means for initiating conduction by these discharge devices at precise times during the respective cycles of phase voltage of the supply circuit 2. These means may comprise saturable peaking transformers I20, I21 and I20 of the type whereby the phase of the output voltage may be controlled by phase shifting means comprising resistances I20, I30 and HI which control the phase of the voltage impressed on the primary winding means. Secondary windings I32, I33 and I34 are connected to grids I35 of discharge devices I23-I25, respectively. Peaking transformer I21 is also provided with an additional secondary winding I30 which is connected to grid I of electric discharge device I00 to control accurately the time at which electri discharge device I03 is rendered conducting wi respect to the voltage of the supply circuit 2.

The discharge device I in the timing means I04 is normally maintained nonconducting by impressing on its grid I00 the negative hold-oil! voltage across resistance I I5 through transformer I31, the secondary winding I30 thereof being connected between the grid I00 and the negative conductor III of the direct current source. The primary winding I30 of transformer I31 is connected in series relation with the anode-cathode circuit of electric discharge device I23 and when energized by the discharge device I23 impresses a positive voltage on grid I09 sufllcient to overcome the effect of the hold-oft potential and initiates operation of the timing means I04.

Discharge device I 23 is normally maintained nonconducting. In order to obtain an impulse of current for energizing transformer I31 and, hence, for rendering the discharge device I05 conducting, I provide a capacitance I40 which is charged from the source of direct current including conducior 'I I0 and I I I through resistance I which constitutes a portion of a volta e divider including another resistance I42. Capacitance I40 is selectively charged and discharged by means of a relay I43 having an actuating coil I44 and contacts I45 and I40. Contacts I40 are the charging contacts which when in the closed circuit position connect capacitande I40 across resistance HI; and contacts I45 are the discharge contacts which when in the closed circuit position connect the capacitance I 40 in series relation with the primary winding I30 of transformer I31 and the anode-cathode circuit of the discharge device I23.

It will be noted that the timing voltage produced by means I04 is impressed on the anodes of the discharge devices I24 and I25 through a conductor I40, and that the potential of the cathodes of the discharge devices 00-43 is determined by a voltage divider including resistances I41 and I43 and which is connected to the source of direct current. The voltage which renders the discharge devices 02 and 03 conductive is derived from the anode of discharge device I00 through a conductor I40; the voltage which renders the discharge devices 30 and 3| conductive is obtained by utilizing the voltage drop across a resistance I50 connected in the anodecathode circuit of the discharge device I24. Resistance I50 is connected to the grids of discharge devices 00 and 0I' through a conductor I5I. In like manner, the grids of discharge devices 00 and 00 are connected through a conductor I52 to a resistance I53 connected in the anode-cathode circuit of the discharge device I25.

Where it is desired to effect only a single energization of the welding circuit I in response to a single circuit controlling operation, the actuating coil I44 of relay I43 may be energized by a manually operable circuit controlling means, such as a switch I54. However, in those applications where it is desired to effect intermittent or periodic energization of the welding circuit I, actuating coil I44 may be periodically energized by eflec'ting such energization of this coil. As a means for accomplishing this periodic energization of coil I44, I have/illustrated a switch I55 which is periodically closed by means of a motor I50 and suitable interlocking or gearing means I51 which may comprise a cam for operating the switch I55.

The operation of the embodiment of rrrv invention shown in Fig. 2 will be explained by considering the system when it is desired to transmit to the welding circuit I a direct current of predetermined magnitude for a definite interval of time. The magnitude of the current transmitted to the welding circuit I is established by the adjustment of the rotary phase shifter I03. The interval of energization is determined by the adjustment of resistance I I1. Peaking transformers I20-I20 are adjusted by means of resistances I20-I3I, respectively, so that the initiation of conduction of current by electric valve means Ii-II occurs at times corresponding to the power factor angle of the load imposed on the supply circuit 2. That is, each of the individual pairs of electric valve means is ad- 'justed to begin conduction during the respective phase voltages at that time corresponding to the power factor angle, thereby preventing the occurrence of starting current transients.

The electric valve means 0-H are normally non-conducting inasmuch as the associated control electric discharge devices 11-02 are maintained nonconducting by virtue of the negative biasing potentials impressed on the grids 03 of discharge devices 11-02. Furthermore, the discharge devices 00-93 in control circuits 05-01 are maintained nonconducting by virtue of the negative potentials impressed on the grids thereof, preventing the application of the peaked voltages produced by transformers 94-90 on the grids 03 of discharge devices 11-02.

Capacitance I40 is charged to the polarity indicated on the drawings from the direct current source by virtue of th voltage drop across resistance MI. The charging circuit of capacitance I40 is completed through contacts I40 of relay I43. Initiation of the period of conduction of the welding circuit I is accomplished by closure of switch I54 which energizes actuating coil I44 and opens contacts I40 and closes contacts I45, the latter contacts connecting the capacitance I 40 in the anode-cathode circuit of discharge device I 23. However, the discharge device I 23 does not necessarily conduct instantly since its grid I35 is maintained at a negative potential by virtue of the voltage drop across by commutating the current from the device 196 which was previously conducting. soon as the discharge device 105 is connects-ted, that is rendered nonconducting, its anode voltage becomes positive as the capacitance H8 is charged in the opposite direction. This rapid raise of anode potential of this discharge device causes a rapid reversal of the normally negative potential applied to the grids of discharge devices 82 and 93 in control circuit 8?. These latter discharge devices are connected to act effectively as a switch so that when conducting current the output of transformer 98 is impressed on transformers l! and 102 and consequently on grids B3 of discharge devices 81 and 82, thereby ultimately effecting energization of control members is of the pair of electric valve means id and H. Thus it will be understood that the primary winding of transformer 42!.- is excited through the reversely connected electr c valve means to and ii at the proper point in tne cycle of associated phase voltage determined by the phase setting of the peaking transformer ME to eliminate any transient in the power transforming means. It should be noted that this point in the cycle will not coincide with the normal conduction initiation point as determined by phase shifter I03, but may be later in the cycle as in the case when the maximum output of the system is desired, or earlier in the cycle when minimum heat or minimum load current or Welding current is used.

As the anode voltage of discha becomes positive it also produces pour age in the anode circuit of discharge devices and B25. These discharge devices, do not begin to conduct current immediately since they are maintained nonconducting by tive biasing potential appearing across 1 N2, and consequently conduction by charge devices is delayed until the proper in stants in the cycles of the associated phase volt ages as determined by the phase position i the voltages of secondary windings. and i i; of peaking transformers t2? and HE, As these two discharge devices are rendered conducting at the proper phase positions, discha e devi M ti and 88 are rendered conducting at sired corresponding angles. The charge devices 90, 91 and 88, B5 effectively connect transformers 59, MB and 51, $8 in circuit with transformers 95, 94 to energize the grids 28 of discharge devices 19, 80 and ll, [8. manner, the electric valve means 8, 9 and B, l are endered conducting at the proper instants during the cycles of the respective associated phase voltages.

After all three sets or pairs of electric valve means have conducted current, electric valve means continue to conduct current in the usual sequential manner determined by the order of phase rotation of the polyphase system of voltages of circuit 2, starting to conduct ent at the proper phase position as determine: 'rotaiy phase shifter E63. This operation continues m long as the anode of the discharge devic 1'06 remains positive. However, the timing capmitance I discharges through a circuit including resistance 52! winding I36 and the lower portion of resistance I22. After a definite time interval, as determined by these circuit constants, the grid of the discharge device I again becomes more positive than the critical grid voltage for this In this assess? this discharge do ice to the discharge device M8 voltage drops imolisl'ies the negative voltage coupling discharge devices w l: in tum. remove the exremainder: of the system. Thus, the next time the alternating current supplied to the system passes through zero, electric valve means 6-H become nonconducting, or whichever pair is then conducting becomes nonconductin'g, and the energization of welding circuit I is terminated. No further current will then be transmitted to the welding circuit l until switch All is released and reset.

It will thus be apparent that with the above arrangement it is possible to employ the system which I disclose in spot welding applications where it is desired to transmit a predetermined magnitude of current to the welding circuit or definite interval of if it is desired to sheet intermittent or periodic energizaticu of the welding circuit 1, the actuat ing coil I of relay I may be periodically or intermittently energized by means of switch I" and motor l58. The speed of the motor Ill is preferably adjusted so that the contacts I" are maintained closed for a period of time somewhat greater than the positive impulse of biasing voltage produced by timing means i. The time that the contacts of switch II! are maintained open will establsb the period of time between each successive energlzation oi the welding circuit 5.

While I have shown and described my inventicn as applied to particular systems or conn c tions and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be departing from my invention, and I, therefore, aim in the appended claims to on or all such changes and modifications as fall within the true spirit and scope of my invention.

Vihat I claim as new and desire to secure by Letters Patent of the United States is:

i. In combination, an. alternating current supply circuit, a load circuit, transforming means, a pair of i-evers .v connected electric valve means connected a id. supply circuit and said transformin or transmitting alternating current the electric valve means comprising control means, an electric inverter energized from supply circuit for producing a periodic electric timing quantity and comprising electric discharge device, means tending to prevent operation of said inverting means, means connected between said inverting means and said control means for supplying energizing potential to said control means when said inverter is oper-- ating, and means for initiating operation of said inverter and for rendering said electric valve means conductive for a predetermined interval of time determined by said timing quantity.

2. In combination, an "I: phase alternating current supply circuit, a load circuit, transforming means comprising 11 winglngs, n pairs of revcrseiv connected electric valve means each connected between dii'ierent phase of said supply circuit and a diiicrent one of said windings, said electric valve means each having a control member for controlling the conductivity thereof, and a plurality of each associated with a different one of said pairs of electric valve means and each connected to the respective control members for rendering said electric valve means conducting in a predetermined order and at times during the respective cycles of phase volt ages corresponding to the power factor angle of the load imposed on said supply circuit.

3, In combination, a polyphase alternating current supply circuit, a load circuit, transform ing means comprising a plurality of winding sections, a plurality of pairs of reversely connected electric valve means each connected between a dinerent phase of said supply circuit and a difi'erent one of said winding sections, said electric valve means each having a control member for controlling the conductivity thereoi, timing means for producing a timing quantity to control the period of energization of said load circult, and means connected between said timing means and the control members of said electric valve means to render each of the Various pairs conducting at a time during the cycle of the associated phase voltage corresponding to the power factor angle of the load imposed on said supply circuit.

4, In combination, a Dolyphase alternating current supply circuit, a load circuit, transforming means comprising a plurality of winding sectlons, a plurality of pairs of reversely connected electric valve means connected between said supply circuit and said transforming means, said electric valve means each having a control memher for controlling the conductivity thereof, timing means for producing an electrical quantity for determining the period of energization of said load circuit, means for producing a polyphase system oi control voltages, and means connected between said timing means and said last mentioned means for rendering said plurality of pairs oi electric valve means conducting at times dur ing the respective cycles of associated phase volt ages corresponding to-the power factor angle of the load imposed on said supply circuit thereby substantially eliminating the starting current transient.

5. In combination, a polyphase alternating current supply circuit, a load circuit, transforming means comprising a plurality of winding sec tions, a plurality of circuit controlling means each connected between a diiierent phase of said supply circuit and a diii'erent one 01' saidwinding sections, timing means for controlling the period of energization of said load circuit, and means rel, sponsive to said timing means for effecting operation of said circuit controlling means and for closing the circuits to the various winding sections at times during the cycles of the respective phase voltages corresponding to the power factor angle of the load imposed on said supply circuit.

6. In combination, a polyphase alternating current supply circuit, a load circuit, transform ing means including a plurality of winding sec tions, a plurality 01' electric valve means con nested between diiiferent phases of said supply circuit and different winding sections, said clec tric valve means each comprising control means, timing means for producing an electrical quantity to control the period of energization of said load circuit, a plurality of control circuits for selectively energizing th control means of said eiec 'tric valve means and each comprising an electric discharge device for controlling the application of energizing voltage to the associated control means, a plurality of individual control circuits connected to operate consecutively in timed. rela tion with respect to the order of phase rotation of the'phase voltages of said supply circuit, and

means connected between said timing means and ing means, a plurality of of being connected between a diiier the last mentioned consaid last mentioned cm a period, of time quantity,

7. In combination, a polypllase current supply circuit, a load circt h or; each pair or? lit conducting during a period n trical degrees of the voltage of; c

8. In combination, a polypiia e r em current supply circuit, a load cir transforming means, a plurality versely connected electric valve supply cimult an said polyp means, said electric valve means e a control member for contr lin t thereof, a plurality of electric all, each associated with differ it c trio Valve nieans ii c elated con rol member thereof i circuit, a means comprising; a plurality o a plurality ele iii, in cornhinaticn, current supply circ "it, ing' a pin nest d electric said, supply pairs during e circuit for l des in t tions, a plural o c each connected between a diiier supply circuit and said wirfng means for cont olling sa ci means to conduct current scone itiate conduction there-by at dorms cycles of the respective associated phase ages corresponding to the power factor angle of the load imposed on said supply circuit.

12. In combination, an n phase alternating current supply circuit, a load circuit, a single phase transforming means each including a primary winding and a secondary winding, 12. pairs of reversely connected electric valve means, said electric valve means and said primary windings being connected in an 'n-sided mesh with each side of the mesh including in series one pair of reversely connected electric valves and the primary winding of one of the transformers, said mesh being connected for energization from said I the output circuits of said biphase rectiflers.

ORRIN W. LIVINGSTON. 

